Method of forming an aluminum article



United States Patent METHOD OF FORIVHNG AN ALUMINUM ARTICLE Philippe D. S. St. Pierre, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York No Drawing. Original application Apr. 8, 1958, Ser. No. 727,053. Divided and this application Mar. 27, 1962,

Ser. No. 182,952

3 Claims. (Cl. 75212) This invention relates to a method of forming aluminum articles and more particularly to a method of forming aluminum articles by powder metallurgy processes.

This application is a division of my co-pending application filed April 8, 1958, as Serial Number 727,053, now abandoned.

While it would be desirable to form aluminum articles, which are used extensively, from aluminum powder by compacting and sintering the powder, such powder will not sinter in a satisfactory manner. The particles of the aluminum powder are covered with aluminum oxide when the powder is formed in contact with air and this results in an unsatisfactory sintered article.

It is an object of my invention to provide a method of forming an aluminum article from aluminum powder.

It is a further object of my invention to provide a method of forming an aluminum article from aluminum powder wherein the aluminum oxide coating on the powder particles is eliminated and a plating metal is deposited on these particles.

In carrying out my invention in one form, a method of forming an aluminum article comprises providing aluminum powder, removing the oxide coating from the aluminum powder in the presence of a dilute solution of a more noble metal, coating the metal on the aluminum powder from said dilute solution, compacting said coated powder, and sintering said coated powder in a non-oxidizing atmosphere such as a neutral or reducing atmosphere.

These and various other objects, features and advantages of the invention will be better understood from the following description.

Aluminum powder is not normally compacted and sintered to produce an article since the oxide film on the powder particles creates a serious difficulty in the sintering step resulting in an unsatisfactory product. The present invention relates to a method of forming an aluminum article from aluminum powder. When aluminum powder is formed or milled from aluminum metal in contact with air, the aluminum oxide coating is removed from the aluminum but reforms instantly on the powder particles. I discovered that when the aluminum powder is formed from aluminum metal with the removal of the oxide therefrom, reformation of surface oxide can be eliminated by milling the powder in the presence of a dilute solution of a more noble plating metal. The plating metal deposits on the surface of the aluminum powder particles eliminating any further oxidation of the powder which would occur subsequent to its formation. The coated aluminum powder is compacted and is subsequently sintered in a non-oxidizing atmosphere such as a neutral or reducing atmosphere to produce the article.

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An example of a method of forming an aluminum article in accordance with the present invention is as follows.

Aluminum powder is submerged in a one percent aqueous copper sulfate solution comprising one gram of CuSO -5H O and 99 grams of water. The powder is milled while submerged in the solution. During milling, the oxide surface is abraded from the powder. Copper from the copper sulfate is electromotively displaced from solution and coats the surfaces of the aluminum powder. The coated powder is then removed from the solution and is compacted and sintered in a neutral atmosphere.

While other modifications and variations of method which may be employed within the invention have not been described, the invention is intended to include such that may be embraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of forming an aluminum article which comprises forming aluminum powder from aluminum metal in the presence of a dilute solution of a more noble metal thereby removing the oxide coating from said aluminum, coating said metal on said aluminum powder from said dilute solution, compacting said coated powder, and sintering said coated powder in a non-oxidizing atmosphere.

2. A method of forming an aluminum article which comprises submerging aluminum metal in a dilute solution of a more noble metal, forming aluminum powder from said aluminum metal thereby removing the oxide coating from said aluminum, coating said metal on said aluminum powder from said dilute solution, removing said coated powder from said solution, compacting said coated powder, and sintering said coated powder in a nonoxidizing atmosphere.

3. A method of forming an aluminum article which comprises submerging aluminum metal in a dilute solution of copper sulfate, forming aluminum powder from said aluminum metal thereby removing the oxide coating from said aluminum, coating said copper on said aluminum powder from said dilute solution, removing said coated powder from said solution, compacting said coating powder, and sintering said coated powder in a nonoxidizing atmosphere.

References Cited by the Examiner UNITED STATES PATENTS 1,214,271 1/1917 Bugbee 204-33 1,457,149 5/1923 Cunningham 204-33 FOREIGN PATENTS 522,463 6/1940 Great Britain.

527,618 10/1940 Great Britain.

REUBEN EPSTEIN, Primary Examiner.

CARL D. QUARFORTH, Examiner. 

1. A METHOD OF FORMING AN ALUMINUM ARTICLE WHICH COMPRISES FORMING ALUMINUM POWDER FROM ALLUMINUM METAL IN THE PRESENCE OF A DILUTE SOLUTION OF A MORE NOBLE METAL THEREBY REMOVING THE OXIDE COATING FROM SAID ALUMINUM, COATING SAID METAL ON SAID ALUMINUM POWDER FROM SAID DILUTE SOLUTION, COMPACTING SAIC COATED POWDER, AND SINTERING SAID COATED POWDER IN NON-OXIDIZING ATMOSPHERE. 